Isoolefin polyolefin interpolymer derivatives and compositions comprising the same



Patented Mar. 17, 1953 UNITED STATES PATENT OFFICE ISOOLEFIN POLYOLEFIN INTERPOLYMER DERIVATIVES .AND COMPOSITIONS COM- PRISI'NG THE :SAME

Richard A. Crawford, Akron, and Richard T. Morrissey, 'Cuyahoga Falls, Ohio, assignors to The B. F.-Goodrich--Company, New York, N.'Y.,

a corporation o'f NewYork No Drawing. Application April 18 1950, SerialNo. 156,724

13 Claims.

This invention relates to novel materials of the class characterized as being 'bromineecontaining derivatives of isoolefin-polyolefin interpolymers,

and pertains particularly to rubbery materials -of this ;class; to the preparation thereof; and 'to compositions comprising the same together "with 7 other materials, particularly other rubbery materials such as natural rubber and the known,

130; 2,373,706; 2,384,975 and 2,418,912andin co- I pending applications Serial No. 651,613, filed March 2, 1946, and Serial No. 166,979 filedJune 6, I950. The presently best known examples of such interpolymers are the copolymers of isobutylene with a small proportion of isoprene or butadiene known to the rubber industry as Butyl (or GR-I) rubber. 7

While 'Butyl rubber has found 'considerable'use in the'manufacture of innertubesyit possesses in-v herent disadvantages which have prevented its more widespread use. It vulcanizes or-cures'more slowlythan other widely used sulfur-vulcanizable rubbery materials; it does not adhere well to other materials including natural rubber, and when it is mixed with natural rubber and the mixture vulcanized the resulting vulcanizatesare generally less valuable than vulcanizates' from either of the rubbery materials alone.

We have now discovered that the introduction of bromine atoms into the polymer structure of Butyl rubber and similar isoolefin-polyolefin interpolymers, so as to produce units of the structure Br Br as by bromination of such interpolymers, ,results in the obtainment of "new materials with properties unexpectedly superior to those of the bromine-free materials. Thus, we have found that brominated rubbery isoolefin-polyolefininterpolymers cure or vu'lcanize quite rapidly, even-with vulcanizing agents which are totally inei fective with the unbrominated materials, to yield vulcanized products which far surpass those obtained from the unbrominated materials in a number of respects including a much greater ability to withstand the effects of heat and aging, and a lower permanent set, and which are fully equal or superior to the vulcanizates from unbrominated materials in other respects such as tensile strength and elasticity, low temperature flexibility and resistance to air-difiusion. "In addition, the' bromina'ted interpolymers, unlike the unbrominated materials, adhere well to a wide variety of materials including natural and synthetic rubbers and are, therefore, of considerable value as adhesives.

We have also found that'the bromine-containing interpolymers may be mixed with natural rubber or any of the various known synthetic rubbers in any desired proportions and that the resulting mixtures co-vulcaniae to give products of excellent properties. .Mixtures of Butyl rubber with small amounts of natural rubber can not be vulcanized to appreciable strength but similar mixtures containing the :bromi-nated interpolymers have high strength and excellent properties. Similarly, brominated interpolymers remarkably improve the ozone resistance, flex resistance and .other properties of natural rubber vulcanizates whereas unbrominated interpolymers so used in natural rubber act only as inertfillers with no significant improvement .in properties.

The bromine-containing isoolefin-polyolefin interpolymers of this invention are prepared, ac-

cordingv to our procedure, by reacting an isoole fin-polyolefin hydrocarbon :interpolymer with a brominating agent. Since the reaction which occurs involves an addition of bromine to olefinic double bonds, the isoolefin-polyolefin interpolymer used must and will, of course, contain .olefinic vunsaturation, but its nature may otherwise be varied widely.

Preferred isoolefin-polyolefin interpolymers for use .in preparing brominated derivatives are the solid plastic rubbery interpolymers described in the above-mentioned patents and patent applications. Among these are, for example, the interpolymers ofa major'proportion, desirably from to 99% by weight, of an 'isoolefin generally containing from 4 to '8 carbon atoms such as, most desirably, isobutylene or, alternatively, 3- methyl butene-l, 4-methyl pentene-l, 2-ethyl butene-l, 4-ethyl pentene-l or the like or a'mixture of such isoolefins, with aminor proportion small amounts of the- 3 desirably from 1 to 30% by weight of a polyolefinic hydrocarbon generally containing from 4 to 18 carbon atoms, or two, three or more such hydrocarbons, including the following:

1) acyclic or open-chain coniugated diolefins such as butadiene-1,3, isoprene, 2,4-dimethy1 butadiene-1,3, piperylene, 3-rnethyl pentadiene- 1,3, hexadiene-2,4, 2-neopentyl-butadiene-1,3 and the like; V

(2) acyclic non-conjugated diolefins such as dimethallyl and its homologs containing 2 to 6 carbon atoms interposed between two isopropenyl radicals, Z-methyl hexadiene-1,5, 2-methy1pentadiene-1,4, Z-methyl heptadiene-1,6, 2-methyl heptadiene-l,4 and other tertiary non-conjugated diolefins having one double bond in the terminal position attached to a tertiary carbon atom;

(3) alicyclic diolefins, both conjugated and non-conjugated, such as cyclopentadiene, cyclohexadiene, l-vinyl cyclohexene-3, l-vinyl cyclohexene-l, l-vinyl cyclopentene-l, l-vinyl cyclobutene-2, dicyclopentadiene, and the like as well as monocyclic diolefinic terpenes such as dipentene, terpinenes, terpinolene, phellandrenes, sylvestrene and the like;

(4) acyclic triolefins such as 2,6-dimethyl-4- methylene-heptadiene-2,5, Z-methyl hexatriene- 1,3,5 and other conjugated triolefins, as well as myrcene. ocimene. alln-ocimene and the like:

(5) alicyclic triolefins such as fulvene, 6,6- dimethyl fulvene, 6,6-methyl ethyl fulvene, 6-ethyl fulvene, 6,6-diphenyl fulvene, 6-phenyl fulvene and other iulvenes oi the formula wherein each R is hydrogen, alkyl, cycloalkyl or aryl; as well as other alicyclic triolefins such as 1,3,3 trimethyl 6 vinyl cyclohexadiene 2,4, cycloheptatriene etc.; and

(6) higher polyolefins such as 6,6-vinyl methyl fulvene (a tetraolefin) and 6,6-diisopropenyl fulvene (a pentaolefin).

Such preferred solid, plastic, rubbery interpolymers are generally prepared by low temperature (temperatures range from 0 C. to -40 C. to '78 C. or to 100 C. or to l27 C. or even as low as 165 C.) interpolymerization utilizing an appropriate catalyst, generally an active metal halide or Friedel-Crafts type catalyst such as aluminum chloride or boron trifiuoride. dissolved in a low freezing solvent such as methyl or ethyl chloride, and, when so prepared, generally possess an average molecular weight above 15,000 and often as high as 30,000 to 120,000 or higher, iodine numbers in the range of 0.5 to 50, and are reactive with sulfur to yield elastic products. Of the preferred interpolymers, we find it most desirable in preparing the brominated derivatives of this invention to utilize the solid plastic interpolymers of isobutylene with small amounts of isoprene or butadiene, of the character of Butyl rubber.

However, it is to be understood that in addition to the preferred materials set forth above, any of the other known isoolefin-polyolefin interpolymers may also be utilized to preparebrominated derivatives having desirable properties not possessed by the unbrominated interpolymers. For example, resinous interpolymers of low molecular weight and/0r not readily vulcanizable with sulfur, yield in accordance with this invention brominated derivatives which possess enhanced adhesive properties, and the ability to be used advantageously in the compounding of rubbery materials. Similarly, isoolefin-polyolefin interpolymers containing other interpoly- .merized monomers such as styrene, chlorostyrenes, acrylyl chloride, methallyl chloride, and other monoolefinic monomers are also advantageously used to prepare brominated derivatives. To illustrate, a brominated interpolymer of 50% isobutylene, 30% styrene and 20% isoprene is superior to the corresponding unbrominated interpolymer as an adhesive and in the compounding of rubbery materials.

In preparing the bromine-containing derivatives of this invention by the bromination procedure, there may be used any desired brominating agent such as molecular bromine itself or the compounds of bromine which liberate molecular bromine among which are sodium hypobromite, magnesium bromide hexahydrate, N bromosuccinimide, alpha bromo acetoacetanilide, beta bromoethyl phthalimide, N bromoacetamide, tribromo phenol bromide, bromo-beta-naphthol, pyridinium bromide perbromide, etc.

Likewise, the bromination may be carried out in any desired manner. One method consists in preparing a solution, dispersion or cement of the interpolymer in an appropriate normally liquid organic solvent or diluent such as a hydrocarbon or halogenated derivative thereof (examples of which are toluene, chlorobenzene, hexane, heptane, trichloroethane, carbon tetrachloride etc.) and adding the brominating agent either as such or in solution, for example, in carbon tetrachloride, to the interpolymer solution, dispersion or cement thereby to form the brominated interpolymer in' solution or dis-. persion in the solvent or diluent. The resulting solution or dispersion may be utilized as such,

as, for example, when the brominated derivative is employed'as an adhesive, or it may be admixed with a non-solvent for the brominated tive thereof which boils below room tempera-;'

ture, say in the range of 30" C. to +20 0., such as methyl or ethyl chloride or butane, and carrying out the bromination at a temperature and pressure such that the solvent or diluent is maintained in the liquid state. This greatly simplifies recovery of the solvent or diluent since the resulting brominated mass can be run into water above the boiling point of the solvent or diluent so that the latter is flashed off and condensed while the brominated interpolymer is precipitated or coagulated in a conveniently handled crumb-like form. In addition, since solid rubbery isoolefin-polyolefin interpolymers are generally prepared by polymerization at low temperatures in such a solvent, use of this variation also permits efiicient and practical integration of the processes of preparing and brominating isoolefin-polyolefin interpolymers.

Another method of carrying out the bromination consists in passing gaseous bromine over a solid isoolefin-polyolefin interpolymer in finelydivided form. Still another method, also appl cable-ao solid:interpolymersnresidesin a solid -=,br0minati ng agent such as nterpolycinimide or 'N-bromoacetamide o the; met on a mixing .-mi1l,,io1lowed by heating the mixture to a "temperature above that at which the brominating agent decomposes to liberate molecular bromine.

Regardless of the particular method employed for efiecting the bromination, it has been'iound that the bromination reaction occurs quite rapidly and essentially involves the additionof bromineto the olefinio 'double'bonds of the interpolymer. :pConsequently the resulting brominecontaining interpolymers possess in their structureunits of the formula I I RCA).-

structure.

The amount of bromine which reacts with the interpolymer during brominationdepends upon the brominating agent being used, the method of bromination and the concentration of brominating agent, but does, not appear to depend greatly upon thetime of reaction. When other factors are-constant there appearsto be an :approximate straight line relationship between the original concentration of available bromineand the amount of bromine vpresent in the brom'inated interpolymer. This is quite advantageous in that the bromine content of the brominated derivative can be controlled-rather closely simply by reg-u'latingthe concentration of the'brominating agent. When brominating in solution in an organic "solvent'using an'initial amount of bromineless than that required to saturatethe interpolymer, it has been observed "that about to 60% of the theoretical amount of :available bromine reacts with the interpolymer.

The brominated interpolymers resulting "from the bromination reaction may contain from as little as 0.5% by weight or to 4, 8, 1001' even 20% by weight orievenas inuchzas 50%tby'weight of combined bromine depending :on the degree of ,unsaturation, which in turn depends upon the proportion of polyolefin, in the particular interpolymer used. Preferably, the percentage of combined bromineis lessthan that which w uld theoretically be present vif all :the olefinic .jdouble bonds LC=:C units) .Welfe completely "I.b Z minatedjto give units, and still more-preferably-for high molecular weight rubbery isoolefinepolyolefi-n interpolymers containing iodine numbersless than 50, of the nature of Butyl rubbeixthe percentage of combined bromineis from 20 to 80%;ofthe amount which would :be ,present if all .olefinic douhlerhcneswereseompletely brcm nated- I wer preferably, the percenta e of no... bromin n such intcrpclyme 11in the ran f .1 to 1 8%. nd ,if r .zadhesire ianp icatiuns is in the :;range .of 1:11 141%- ;Fr the :ferescing is apparent that the pref rred abr rnina ed zin erpe yme s f :this invention are not completely saturated but that hey ar less uns tura ed than the parent unbromineted .aintnrpclymers. flheir :molecular We ghts are .-of :the same order as the parent nbrorninat d :interpclymer :but are enera1ly somewhat higher because of the presence oft'the relatively heavy bromine watoms.

,Brominaticn of vis o'l fm-r.mlyolefii-i "interna imer so as to :Droduce rial.

' l r l3-r unitsis not ,the 'onlymethod of arriving at interpolymers containing such units, but is at present preferred. Another {method consists in interpolymerizing an isoolefinic monomer with a polyo'lefinic monomer at "least one :of which monomersisbromi-nated*soas tocontainthe structure. For example, the interpolymerization o is hut lenewwitn -d br mc:bu asi n which has-the JBrBr un in its..-structure;pi

11851111331111LhG-PIOGUCtiOnQf an interpolymer containing 251-1011 units; this interpolymer, however, is more unsaturated for a given bromine-content than iarezthe bromine-icontai-ning intenpoiymersproduced by bromination :of isoolefinedioleyinterpolymers.

.;As :mentioned :hereinabove, 'ithe ;properties of the bromine-containing interpoly-mers of this invention are quitequ-niq-ue. The brominated-derivat-ives :of. solid gala-stir: :nubbery interpolymers are themselvessolid plasticviubbery materials which possessthe -a,dvantages .;of the parent :unbrominated materialsiand in addition arejar superior with respect to (adhesive properties, ease of -:v,ulcanization, and various properties of the vulcanizates. ,They'may 'be used forallof the .purposes for which the ;unbrominate.d :rubbery interpol-ymers 1 are :usef-ul ias, for example, .--for the manufacture of, inner tubes, :tire-curingbags, ;etc,,,, and they-may be used for various :purpose s, ,o,f particular importance in manufacture of- I andsa Lrnultitude of other rubber products, which the unbrominated ,materials are unsatisf ory. flor examr e hey-m y rb used asz dhesives bcn :..-rub er i materi ls-t e ch the being esp cia l u eful :in bondin the i br ma i olefin-pcly l n .i erp lymers-to each ,1 other, to :natural rubberwandnto ;die ne ,synthetic rubbers. filmy-may also be used uite-a1 vantageously in vulcanizable admixtures in any desired proportion with-natural rubber and diene sy h i -rub ers; impartingv h desir ble .p operties-oirem rk blv increased-rezo e resistan e i prove resistanc to flexin and .inc a ed resistance to air diffusion to ,the 1 resulting vulcanizates. :In .any .of .these v.uses they .may Jae compounded with any of the conventional ingredients used in compounding th unbrominated rubbery isoolefin-polyolefin interpolymers or other rubbery materials, and they may be vulcanized by the same general methods. Their vulcanization proceeds much more rapidly than that of the unbrominated materials, despite their generally lower degree of unsaturation, and they may be vulcanized in the absence of sulfur with agents, such as the bivalent metal oxides particularly zinc oxide, which are ineffective in vulcanizing the parent unbrominated interpolymers.

The preparation, properties, compounding, vulcanization and use of the brominated interpolymers of this invention are more fully set forth in the following examples which are intended as illustrative only-since numerous modifications and variations therein will be apparent to those skilled in the art. In the examples, all parts, unless otherwise specified, are by weight.

" Example 1 A high molecular weight, solid, plastic copolymer of, about 97% isobutylene and 3% isoprene is dissolved in liquid ethyl chloride to form a 20% solution containing 100 parts of copolymer. The solution is made up in a closed reactor equipped with stirring means and with means for maintaining the ethyl chloride in the liquid state. A solution containing 5 to 16 parts of bromine dissolved in ethyl chloride is added to the copolymer solution by injection or from a bomb under nitrogen pressure and the resulting mixture is stirred for one hour. An excess of sodium carbonate as a to 30% solution in water is then added to neutralize any unreacted bromine. After further stirring for less than 1 hour a slurry of finely-divided calcium silicate in water is added. Following further stirring for minutes, the reaction mixture is transferred to a closed coagulating tank containing hot Water (60-'70 C.) and a colloidal protective agent (which may consist of about 5 parts of finelydivided calcium silicate), whereupon the ethyl chloride'is flashed off and condensed by means of a suitable condenser attached to the lid of the coagulating tank. The brominated copolymer remains in the form of rubbery crumbs dispersed in the aqueous medium (the calcium silicate 'or otherprotective agent serving to prevent agglomeration of the crumbs) and is separated by filtering or any other convenien method.

The brominated isobutylene-isoprene copolymer thus obtained contains 1.5 to 6.0% of combined bromine (depending on the amount of bromine used) and is a plastic easily-Worked rubbery material. Similar brominated copolymers are likewise obtained when the isobutylene-isoprene copolymer is first formed in situ in the ethyl chloride solution by copolymerization of the mixed monomers at temperatures of 50 to -125 C. in the presence of aluminum chloride as catalyst. In this event the excess sodium carbonate solution added after addition of bromine serves to destroy not only the unreacted bromine but also the aluminum chloride catalyst.

Example 2 tion with stirring in about 1 hour. The resulting reaction mixture is then poured into methanol to coagulate the brominated copolymer which is then separated and washed free of uncombined bromine and hydrogen bromide with sodium carbonate solution in water. The brominated copolymer thus obtained is a solid, plastic rubbery material containing 2.5 to 3.0% of combined bromine.

Example 3 A sample of the isobutylene isoprene copolymer of Example 2 is brominated by passing gaseous bromine over the shredded polymer. This is done by distributing 62 grams of the'shredded copolymer evenly throughout the side arm of a modified distilling flask attached to a receiver immersed in an ice water bath, and distilling ml. of bromine through the flask over the polymer and into the 'cold receiver for a period of 30 minutes.

Bromination of the copolymer is detected by color change in the copolymer.

tain about 3% of combined bromine.

' Example 4 12 parts of N-bromo succinimide and 100 parts of the isobutylene isoprene copolymer of the pre-' ceding examples are thoroughly mixed by mil1-' ing on a rubber mill and the resulting mix heated for 30 minutes in a circulating air oven maintained at C. The resulting product is a brominated isobutylene isoprene copolymer having properties generally equivalent to the brominated copolymers of the preceding examples. Its bromine content corresponds substantially to the theoretical value.

Example 5 Example 1 is seven times repeated using instead of the isobutylene isoprene copolymer, high molecular weight plastic isoolefin-polyolefin interpolymers as follows:

In each case rubbery plastic brominated interpolymers are obtained containing an amount of combined bromine from 40 to 60 of that used in the bromination.

Example 6 A series of cements each containing 100 parts of the isobutylene isoprene copolymer of EXam-.

The brominated co polymer is washed and dried and found'to con-f 9 this test the unbrominated isobutyle'ne' isoprene copolymer composition and the natural rubber composition are each sheeted out and coated with the brominated cements after which the cemented surfaces are pressed together and the assembly vulcanized. The adhesion expressed in pounds per inch-Width between thetwo compositions is then measured on'the Cooey autographic adhesion tester.

The-following tableshows the per cent bromine added to the cement, the per cent bromine combined with the interpolymer and the adhesion in lbs/inch width between the two rubbery compositions:-

TABLE I- Wt. Percent Br iii Interpolymer 1 (Analysis) I Adhesion, Lbs/Inch Width Wt. Percent Bra Added to Cement Cement No.v

' OOQUIOUI When no adhesive is used between the two compositions the adhesion is less than- 0.5 lbi/inch Width. The use of cements containing unbrominated copolymer likewise results in very poor adhesion. It is quite apparent from the table, however, that the brominated interpolymer'is aremarkably excellent adhesive; Similar excellent adhesions are secured when the rubbery compositions are varied; for example, when a vulcanizableGRL-S- (rubbery butadiene-IBstyrene copolymer) tire-tread composition is substituted for either of the t'Worubbery com-positions;

Example 7 The procedure of Example. 6 isrepeate'd in the same manner as with cement: No. 6' except that the isobutylene-isoprene copolymer used is one which has been previously vulcanized and reclaimed by mixing the vulcanized scrap with dipentene and then heating in steam at 1'75 lbs. steam pressure. The adhesion is again 30' lbs/in; width. thereby demonstrating. that-the interpolymers'used to prepare the brominated derivatives of this invention can be reclaimed before use in this" invention.v

Example 8 The bromin'ate'd interpolymer of Example 3 is compounded on a mixing mill in the following recipe:

Parts Brominated interpolymer m 100 Carbon black 40 Zinc oxide 5 Stearic acid 3 Mercaptobenzothiazole 0.5 Tetramethyl thiuram disulfide 0 .2 5 Sulfur 2.0

The compounded composition is then made into a. cement using gasoline as the solvent and the cement tested as an adhesive for bonding natural rubber to unbrominated isobutylene isoprene copolymer as described in Example 6. An adhesion of 34 lbs/inch Width is obtained;

Example 9 A plastic rubbery interpolymer of 97% isobutylene and 3% isoprene brominated to contain 3.5% of combined bromine, byany or the methods of Examples- 1 to 5, is compounded with 10 40' partsof carbon-black and5 parts of zinc-oxide, each based on -parts of thebrominated interpolymer. The resulting composition is" then heated at 307 F. whereupon vulcanizationor curing occursto form anelastic product asshown in the following table:

TABLEJE sfensigsil gamete reng o gaw Cure at 307 F. (lbsj/s'q ti n in.) (Percent) This" example demonstrates" that zinc" oxide alone (no sulfur) vulcanizes the-brominated interp'olymers of this invention. other bivalent metal oxides such as lith'arge,vv cadmium oxide,.etc. function' similarly. Similar results are also secured using. other plastic rubbery bromin-ated isoolfiiipolyolefin interpolymers containing 2th. 10% or other concentrati on of bromine. NO vulcanization or cure occurs, however, with the unbrominat'ed interpolymers' when heated'witli a metallic oxide as thesole Vulean'iz'ing agent;

Example 10 A" bromi'nated' isobutylene isoprene" interpolymer containing, 3:693 bromine is compounded" in the following recipe:

Parts Bromin-ated' interpolymer 100 Carbon black 40 Zinc. Oxide 7.0 Stearic acid 4.2 2 -mercaptobenzothiaZole 017' Tetramethyl thiuram disulfide 0.35 Sulfur 2.8

Percent Percent Free Combined Sulfur Sulfur:

Unbrominated Interpolymer 0.05 1'. 51 Brominated interpolymer l. 1.26 I 0. 44

Thus; despite the lower unsatur'ation of the brominated interpolymer (as Shown by lower combined' sulfur. in. the vulcanizate) it. vulcanizes much more rapidly than the corresponding-I Ulribrominated. material. v

Other samples of. the vulcanized"composition-s are. aged'. 16" hours at 300 FL and their. tensile strength again measured. The unbrominated interpolymer vul-canizate loses 89% of its tensile strength and becomes quite soft on aging whereas the brominated" interpolymer lose'sonly 67% of its tensile strength and retains its normal} appearance. Accordingly, the cured brominated interpolymers are much more resistant to high temperatures than are the cured unbrominated interpolymers. M This fact is also shown by another test performed on still other samples of the two vulcanized compositions. In this test each sample -is placed under 40% compression at 250 F., and

the stress required to maintain this compression is measured as a function of time. With the cured unbrominated material the required stress is reduced 50% in 2 hours whereas 20 hours are required for 50% reduction in stress with the cured brominated interpolymer. The latter material is therefore much more valuable for use under conditions of compressive stress as in gaskets, seals, suspension systems, etc.

Example 11 a T 1 E t urea ensi e onga ion 00131905113011. 320 F., Time, lbs/sq. Percent 7 Minutes 7 Air Diffusion, ftfiX Composition l0- /day/in.

100% Natural Rubber 0. 00544 80% Natural Rubber 0 00418 20% Brcminated lnterpolymer 50% Natural Rubber 0 00191 50% Brominated interpolymer The inability of the unbrominated rubbery isoolefin-polyolefin interpolymers to co-vulcanize with natural rubber has been one of the greatest disadvantages to the use of such interpolymers. As shown by this example, however, the brominated interpolymers of this invention are completely free from this disadvantage and in addition impart valuable properties to natural rubber vulcanizates.

Example 12 Aseries of white rubbery compositions suitable for use in white sidewall tires etc. are prepared 12 from natural rubber admixed with isobutylene isoprene interpolymers of varying bromine content prepared as in Example 1. The compositions contain the following ingredients:

Parts Rubbery material Zinc oxide 87 Titanium dioxide 14 Ultramarine blue 0.2 Stearic acid 1.5 Z-mercaptobenzothiazole 0.75 Diphenyl guanidine 0.25 Sulfur 2.5

When the rubbery material is made up of 60% of the interpolymer and 40 of natural rubber, the following table shows the variation in physical properties of the resulting vulcanizates with bromine content of the interpolymer, each composition being vulcanized to optimum cure at 320 F.

A Tensile Modulus at Percent Bromide in strength Elongation 300% E1011- Interpolymer (um/Sq. in.) (Percent) absgagilonin Again, it is apparent that the brominated interpolymers yield good vulcanizates in admixture with natural rubber whereas this is not the case with the unbrominated materials.

Other tests on similar compositions show that various improvements are secured by the presence of the brominated interpolymer. For example, vulcanized compositions containing interpolymer with 2.5% combined bromine and natural rubber are prepared by vulcanizing compositions containing these rubbery materials in the following proportions:

The tests show that vulcanized compositions A, B, C and D are superior to composition E in heat resistance, ozone resistance and flexing resistance. Composition E loses 75% of its original tensile strength when aged for'8 hours at 300 F. whereas composition A retains 50% of its tensile strength under the same aging conditions. Moreover, composition A withstands 230,000. fiexures (as measured by the De Mattia procedure) before cracking as against 67,000 flexures for composition E. When the vulcanized compositions are placed in an'oven at 100 F. and exposed to concentrated ozone, the following results are secured:

Hours to 1st Crack Composition Accordingly, this example also illustrates that the properties of natural rubber vulcanizates can be greatly improved by the presence of the broinvention. These improvements; are not secured i when using. unbrominated' interpolymers; rather,

as has been noted above, such materials do not yield satisfactory vulcanizates inadmixture with natural rubber.

The natural rubber used in Examples 11 and 12 abovemay be replacedby' diene synthetic rubbers including polychloroprene, polybutadiene, polyisoprene and copolymers of chloroprene, butadiene or isoprene with each other or with monoolefinic monomers such as styrene, acrylonitrile, acrylic and methacrylic acids and their alkyl esters, vinyllpyridine, vinylidene chlorideand the like, with generally equivalent results. Consequently, this invention includes compositions comprising a brominated isoolefin-diolefin interpolymer in admixture in any desired proportion with any other unsaturated, vulcanizable rubbery material; Such mixtures maybe madeby blending the rubbery materials on a mill or in any internal mixer or by blending solutions or dispersions of the brominated interpolymers with solutions, latices or dispersions of the other rubbery materials, or by any other: desired. method.

From the foregoing description of the invention, it will be seen that brominated isoolefinpolyolefin interpolymers constitute a new, improved and Widely useful class of materials. It is apparent, therefore, that various embodiments of the invention, in addition to those specifically disclosed, may be provided Without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. A solid, plastic polymer of a molecular weight above 15,000 composed of atoms of carbon, hydrogen and bromine, containing in its structure a major proportion of saturated hydrocarbon units derived by the polymerization of an isoolefin containing 4 to 8 carbon atoms and a terminal methylene group, and also containing bromine-containing units of the formula and units in which a pair of carbon atoms is linked by an olefinic double bond.

2. A solid, plastic partially-brominated interpolymer of a major proportion of an isoolefin containing 4 to 8 carbon atoms and a terminal methylene group with a minor proportion of a polyolefinic hydrocarbon, said brominated interpolymer retaining a portion of its original olefinic unsaturation and containing bromine in an amount of at least 0.5% by weight.

3. A solid, plastic, rubbery interpolymer of a major proportion of isobutylene and a minor proportion of a polyolefinic hydrocarbon selected from the class consisting of acyclic and alicyclic diolefins and triolefins, which interpolymer is brominated to an extent such that it contains combined bromine in an amount from 20 to 80% of that required to saturate all of its olefinic double bonds.

4. A brominated, plastic, rubbery olefinicallyunsaturated interpolymer of '70 to 99% by weight of isobutylene and 1 to 30% by weight of an aliphatic conjugated diolefin, said brominated interpolymer containing a combined bromine content above 0.5% by weight but below that which corresponds to complete saturation of the olefinic bonds.

5. A brominated, plastic, rubbery interpolymer of about 97% isobutylene and about 3% isoprene,

- said. brominated: interpolymercontaining a com.

dined-bromine content of l to 4% by weight.

6; A vulcanizable composition of matter comprising a vulcaniz-ing'amount of sulfur in admixture with a solid, plastic, rubbery, partially-brominated. olefinically unsaturated interpolymer of amajorproportion of an isoolefin containing 4 to 8 carbon atoms and a terminal methylene group with a minoriproportion' of a polyolefinic hydrocarbon selectedfrom the class? consisting of' acyclic: and; alicyclic diolefins and triolefins, saidlbrominateda interpolymer containing. a combined: bromine content above 0.5% by weight but below that which corresponds to complete saturation of the olefinic-bonds.

7. A composition of matter comprising a rubbery diene polymer and a solid, plastic, rubber-y, partially-brominated olefinically unsaturated. interpolymer of a major proportion of an isool'efin containing from 4' to 8" carbon atoms and a terminal methylene group with a minor proportion of a polyoiefinic hydrocarbon selected from the class consisting of acyclic and alicyclic diolefins and; trio'lefins, said interpolymer containing a bromine content above 0.5% by weight but below that which corresponds tocomplete saturation of the olefinic bonds;

8'. A composition of 'matter comprising natural rubberanda solid,plastic, rubbery, partially-brominated olefinically unsaturated interpolymer of a major proportion of an isoolefin containing from 4 to 8 carbon atoms and a terminal methylene group with a minor proportion of a polyolefinic hydrocarbon selected from the class consisting of acyclic and alicyclic diolefins and triolefins, said interpolymer containing a bromine content above 0.5% by Weight but below that which corresponds to complete saturation of the olefinic bonds.

9. A composition of matter comprising natural rubber and a brominated plastic rubbery interpolymer of to 99% by weight of isobutylene and l to 10% by weight of an aliphatic conjugated diolefin, said brominated interpolymer containing a combined bromine content of 0.5 to 10% by weight.

10. A vulcanizable composition of matter comprising about 5 parts by weight of zinc oxide admixed with about 100 parts by weight of a brominated plastic rubbery interpolymer of 90 to 99% by weight of isobutylene and 1 to 10% by weight of an aliphatic conjugated diolefin, said brominated interpolymer containing a combined bromine content of 0.5 to 10% by weight.

11. The method which comprises reacting (l) a solid plastic olefinically unsaturated interpolymer of a major proportion of an isoolefin containing 4 to 8 carbon atoms and a terminal methylene group with a minor proportion of a polyolefinic hydrocarbon selected from the class consisting of acyclic and alicyclic diolefins and triolefins with (2) a sufiicient amount of a brominating agent to brominate from 20 to 80% of the olefinic double bonds in said olefinically unsaturated interpolymer by addition of bromine thereto, and recovering the resulting brominated interpolymer in the form of a solid plastic rubbery material containing combined bromine preslinkages and also containing residual olefinic double bonds.

12. The method which comprises dissolving a solid plastic rubbery olefinically unsaturatedinterpolymer of a major proportion of an isoolefin containing 4 to 8 carbon atoms and a terminal methylene group with a, minor proportion of a polyolefinic hydrocarbon selected from the class consisting of acyclic and alicyclic diolefins and triolefins, in a liquid solvent therefor, adding to the resulting solution an amount of bromine less than that required to saturate the olefinic double bonds in said interpolymer whereby from about 20 to 60% of the available bromine reacts with said interpolymer to form a brominated interpolymer containing combined bromine present in linkages and also containing residual olefinic double bonds, and thereafter separating the said brominated rubbery interpolymer from the solution and from unreacted bromine.

13. The method which comprises preparing a mixture of liquid ethyl chloride with a solid plastic rubbery olefmically-unsaturated interpolymer of a major proportion of isobutylene with a minor proportion of an aliphatic conjugated diolefin, adding bromine to the mixture whereby a part of the added bromine reacts with the said interpolymer to form a brominated interpolymer containing combined bromine present in linkages and also containing residual olefinic double bonds, thereafter neutralizing unreacted V bromine in said mixture and adding the resulting mass to Water containing a colloidal protective agent, the said water being at a temperature above the boiling point of ethyl chloride, to flash off the ethyl chloride and produce an aqueous slurry of solid particles of said brominated interpolymer.

RICHARD A. CRAWFORD.

RICHARD T. MORRISSEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,242,586 Ostromislensky Oct. 9, 1917 2,467,322 Lightbown et a1. Apr. 12, 1949 FOREIGN PATENTS Number Country Date 476,269 Great Britain Dec. 6, 1936 OTHER REFERENCES Gallo et a1.: 1277-1280 Ind. and Eng. Chem., July 1948. 

1. A SOLID, PLASTIC POLYMER OF A MOLECULAR WEIGHT ABOVE 15,000 COMPOSED OF ATOMS OF CARBON, HYDROGEN AND BROMINE, CONTAINING IN ITS STRUCTURE A MAJOR PROPORTION OF SATURATED HYDROCARBON UNITS DERIVED BY THE POLYMERIZATION OF AN ISOOLEFIN CONTAINING 4 TO 8 CARBON ATOMS AND A TERMINAL METHYLENE GROUP, AND ALSO CONTAINING BROMINE-CONTAINING UNITS OF THE FORMULA 